The term 'Sneakily Dangerous' can be summed up as 'INSIDIOUS, ' which is a nine-letter word meaning 'intended to entrap or beguile.' It is often used to describe something that is subtle and deceptive, yet still dangerous. Insidiousness can refer to a person's behavior, a situation, or an object. It is often used to describe a person who is slyly manipulative or a situation that is full of hidden risks.